Curing machine for producing tires for road vehicles and the like

ABSTRACT

Two opposed coaxial discoidal elements ( 35, 37 ) are diametrically dilatable and are able to move independently of each other axially and pass axially into the tire (P) when the tire is positioned in the mold, in such a way as to dilate each of said discoidal elements ( 35, 37 ), for engaging a corresponding annular bead (P 1,  P 2 ) of the tire and positioning it exactly against the edge of the respective pan ( 13, 15 ).

The subject of the invention is an improved machine for curing the greenrubber of tires, its main object being the positioning of the greentire, which generally tends to deform—and so cause defects—when placedin the open mold of the curing press.

These and other objects and advantages will become obvious in the courseof the text which follows.

The machine comprises a mold with two circular pans or end plates andperipheral sectors defining the tread, and with bladder means forcreating a pressure inside the tire.

According to the invention, the machine comprises:

two opposed diametrically dilatable coaxial discoidal elements that areable to move axially independently of each other and to pass axiallyinto the tire when the tire is positioned in the mold;

control means for dilating each of said discoidal elements, for engaginga corresponding annular bead of the tire and positioning it exactlyagainst the edge of the respective pan;

means for supplying a shaping gas at limited pressure into the tirewhile the two pans are being moved toward each other during moldclosure; and

means for discharging at the appropriate time the fluids from inside thetire and from the sucker means.

These discoidal elements in practice have sectors that can be movedradially by said control means and contact surfaces for engaging theannular beads of the tire.

The sectors are radially movable and can be operated by shaped linkspivoting on an angularly movable actuator disk coaxial with saiddiscoidal elements.

The discoidal elements may have spring-loaded pegs for making contactwith the inner edge of the annular beads of the tires and able toretract on contact with the circular pans or end plates of the mold whensaid discoidal elements approach the respective circular pans or endplates of the mold.

For bringing about the axial movements of said discoidal elements theremay be provided: a first actuator for lowering both of said discoidalelements into the tire, and raising them again; and a second actuatorfor axially moving one of said discoidal elements with respect to theother.

Advantageously, the control means for dilating each of said discoidalelements are able to bring about a partial dilation before the axialmovement to contact the respective annular bead of the tire, followed bya further dilation to make radial contact with the edge of said bead, bymeans of said spring-loaded pegs.

The bladder means are in practice tubular in shape, with the two annularedges engaged on movable members of two axial actuators capable ofpositioning the bladder means in the mold in the closed position; meansare provided for supplying a fluid—especially a liquid—at pressure intothe bladder means for the molding and curing stage.

Said axial actuators may be cylinder-and-piston systems; one of saidaxial actuators may be in the form of a cylinder-and-piston system whichlifts the bladder assembly and the other of said axial actuators maycomprise two symmetrical toggles controlled by a gear pair mechanismcontrolled by a single fluid actuator.

A clearer understanding of the invention will be gained from thedescription and the accompanying drawing, the latter showing apractical, non-restrictive example of an embodiment thereof. In thedrawing:

FIGS. 1–6 are general views of the machine in six initial stages ofloading the tire leading up to the heat-treatment position;

FIGS. 7, 8 and 9 show schematic plan views of the stages of FIGS. 1 and2; 3 and 4; and 5 and 6;

FIGS. 10–21 show the upper assembly of the machine in vertical crosssections (FIG. 10 being on a larger scale than the others), during thestages of loading the green tire, and up to the stage of partial closureof the mold, and for curing;

FIGS. 22 and 23, 24 and 25, and 26 and 27 are plan views on planesXXII—XXII and XXVII—XXVII as marked in FIG. 11, to illustrate thepositions of the parts in the stages shown in FIGS. 10 and 11; 12–14;and 15–18;

FIGS. 28–31 show, in a similar way to FIGS. 10–21, stages following theheat treatment for discharging the tire;

FIGS. 32, 33 and 34 show partial enlargements of FIGS. 22 and 24 and ofthe dilatable discoidal elements;

FIGS. 35–44 show a first elastic bladder system for applying theinternal compression for curing and unloading in the various stages ofthe relevant cycle; and

FIGS. 45–54 show a second elastic bladder system for applying theinternal pressure for curing and unloading in the various stages of therelevant cycle.

In the drawing, referring initially to all FIGS. 1–9, the referencenumber 1 denotes a horizontal conveyor for feeding green tires P to themachine, the latter having the general reference 3; reference number 5is a general label for individual supports carried by the conveyor 1.Each support 5 comprises a plurality of arms 5A which pivotspontaneously or under control, the job of which is to engage the topedge P1 of the green tire P that is to be conveyed to the machine 3 withmovements indicated by the arrows f1 (FIGS. 7–9) which show thedirection of movement of the conveyor 1. These arms 5A are also designedto act on the lower edge P2 of the tire, the two edges P1 and P2 formingthe annular beads typical of tires for road vehicles. The machine 3comprises a collecting mechanism 9 which has a plate 9A which, as itrises, picks up whichever support 5 has reached the position above thecollecting mechanism 9 with the tire P and, as it descends, lowers saidtire P onto an annular pan 11 which is positioned at the right momentunderneath the tire and will then transfer said tire into the machine 3in line with and underneath the upper assembly 3A (described later) ofthe machine 3. The handling means of the annular pan 11 are notdescribed as their construction is obvious. The collecting mechanism 9is able to raise the support 5 without its tire P and hang it back onthe conveyor 1, which thus takes said support 5 away for subsequentloading of another tire. Feed operations are thus performed cyclicallyas each heat-treatment cycle is completed.

The machine 3 comprises, in addition to said upper assembly 3Aexhaustively illustrated in FIGS. 1–34, a lower assembly which is madein two different embodiments. One version of said lower assembly 3B issketched in FIGS. 1–4 and shown more particularly in FIGS. 35–44, whileFIGS. 45–54 show a different version of said lower assembly. The upperassembly 3A is illustrated in FIGS. 1–34.

The machine 3 comprises a mold consisting of two circular pans or endplates, one upper 13 and one lower 15, and of peripheral sectors 17capable of being moved inward and outward to close and reopen the mold,while the two pans or end plates 13 and 15 can be moved inward andoutward in vertical axial directions. The configuration of the moldoperating mechanisms are of a type known per se, except for the functionthat is to be given to each mechanism for the sequences of the operatingcycle of the machine, which will be described below.

The upper assembly 3A of the machine 3 comprises a structure 23 beneathwhich the upper pan or end plate 13 of the mold is fitted. Housed insidea cylindrical wall 23A of the structure 23 is a large cup 25, from thebottom of which there extends the cylinder 27A of a vertical actuator27, the rod 27B of which piston supports at its upper end a plate 29capable of being moved vertically by the actuator 27. The plate 29 hasrods 31 supporting the cylinder 33A of an actuator 33, whose piston 33Bis integral with a tubular piston rod 33C. The actuator 33, 33A, 33B,33C can be moved vertically by the movements of the plate 29 broughtabout by the actuator 27, 27A, 27B. The cylinder 33A of the actuator 33can slide through the bottom of the cup 25 and supports at its lowerend, beneath said cup, a first discoidal element 35 which is capable ofdiametrical dilations and will be described later. A second discoidalelement 37, essentially symmetrical and similar to the previous suchelement, is supported however by the tubular rod 33C of the piston 33Bof said actuator 33: the second discoidal element 37 can therefore bemoved with respect to the first discoidal element 35 by the actuator 33,which can move its piston 33B and therefore its rod 33C and hence thediscoidal element 37 with respect to the cylinder 33A on which the firstor upper discoidal element 35 is mounted. The actuator 27 is thereforeable to move both discoidal elements 35, 37 simultaneously to variouspositions with respect to the circular pan or end plate 13 of the mold,as can be seen by comparing the sequence of FIGS. 23–27 and 27–31. Theactuator 33 in turn is capable of moving the discoidal element 37 withrespect to the discoidal element 35, thereby moving the two discoidalelements 35, 37 toward and away from each other as can be seen again bya comparison of FIGS. 22–27 and 28–31, and as will be described infurther detail when explaining the operation of this assembly.

The two discoidal elements 35, 37 are essentially equivalent and onlyelement 35 will be described with particular reference to FIGS. 22 and24.

The plate 29 (which can be moved vertically by the action of theactuator 27) has its own cylinder-and-piston actuator 39 which pivots at41 on the plate 29 and possesses, at the end of its piston rod (see inparticular FIGS. 23, 25 and 27), a pivot 43 for a crank 45. This isintegral with a vertical shaft 47 which can thus be controlled by theactuator 39 to make limited angular movements. At its bottom end, theshaft 47 comes to a drive 49 (see also FIG. 34) which imposes angularmovements on a plate 51 on which there pivot at 53 a plurality of shapedlinks 55 (see also FIGS. 32–34). Formed on the discoidal element 35 area plurality of radial guides 57, along each of which runs a slide 59,and on the outer end of the slide is a flat sector 61 to which isconnected at 63 the opposite end of a corresponding shaped link 55 fromwhere it pivots 53 on the plate 51. Rotation of the plate 51 changes theangle of the links 55, which causes a radial excursion of thecorresponding slides 59 and their sectors 61, in centripetal andcentrifugal radial directions. Each sector 61 has a pair ofspring-loaded pegs 65: these are parallel to the axis of axial movementof the discoidal elements 35, 37 and are stressed elastically to projectand can withdraw inside their respective sector 61.

The shaft 47 has a splined section 47A in angular but not axialengagement with a crank 71 corresponding essentially to the crank 45 andperforming the same angular movements as the latter and as the shaft 47and drive 49. The crank 71 forms part of a parallel-motion mechanism 73which transmits the angular movements of the shaft 47 to a shaft 75inside the tubular shaft 33C forming the rod of the piston 33B of theactuator 33, with respect to which the shaft 75 is completelyindependent while it can slide vertically with respect to the tubularrod 33C of the actuator 33. In effect the shaft 75 describes angularmovements identical to those of the shaft 47 of the drive 49 and saidshaft 75 transmits these angular movements to a plate 77 connected tothe discoidal element 37 in a similar way to the plate 51 connected tothe discoidal element 35. The plate 77 has pivoting on it at 79 a numberof shaped links 81 similar to the links 53 which in turn pivot onsectors 83 similar to the sectors 61 with spring-loaded pegs 85extending in the opposite direction to the spring-loaded pegs 65 on thesectors 61.

Basically, the two dilatable discoidal elements 35, 37 are practicallyand functionally symmetrical with respect to a plane perpendicular tothe axis of the central shafts 33C, 75 of the upper assembly 3A. The twodiscoidal elements 35 and 37 are operated symmetrically as regards themovements of the sectors 61 and 83 of the mechanisms described, from theactuator 39 which controls the shaft 47. This actuator 39 can induceangular movements in the shaft 47 in at least two stages and at leasttwo successive strokes, in at least the direction that brings about thecentrifugal movements of the sectors 61 and 83 for the purposesdescribed below and which relate basically to the centering of theannular beads P1 and P2 of the tires P.

FIGS. 22, 24 and 26 indicate the positions adopted by the sectors 61 andsectors 83 in the conditions of smallest diametrical dimension, which isvery close to the maximum diametrical dimension, and of maximumdiametrical dimension; FIGS. 32 and 33 show enlargements of FIGS. 22 and23, and FIG. 24 corresponds to a position of enlargement of the sectorsthat are slightly less than the maximum illustrated in FIG. 26, forreasons indicated later.

Referring more particularly to FIGS. 10–21, these show main stages inthe operation, from loading of the green tire presented to the machine 3as indicated in FIG. 1, to closure of the mold as shown in FIG. 5 and asshown also in FIG. 21 before the sectors 17 of the mold are moved in.

From the position shown in FIG. 1 and therefore also FIG. 10, this isreferred to as an initial stage in which the two dilatable discoidalelements 35 and 37 are withdrawn between the bottom of the cup 25 andthe upper pan or end plate 13 of the mold. The green tire P ispositioned by the annular pan 11 in the position shown in FIG. 11. Inthe second stage the actuator 27 lowers the assembly of the twodilatable disks 35 and 37 into the tire P. In the third stage, FIG. 12,the actuator 39 causes an initial dilation of the discoidal elements 35and 37, moving the sectors 61 and 83 to an almost but not quite fullydilated position: in this position the sectors 61 and 83 are capable ofreaching the beads P1 and P2 of the tire P in order to positionthemselves inside them. In the fourth stage shown in FIG. 13, theactuator 27 raises both discoidal elements 35 and 37, still close toeach other, until the sectors 61 touch the annular bead P1 of the tire,thus raising the tire until it almost reaches the pan or end plate 13.The bead P1 is at a slight distance from the pegs 65 but resting on thesectors 61, in a condition which need not actually be perfectlyconcentric. In the fifth stage shown in FIG. 14, the actuator 33, 33A,33B separates, that is lowers, the discoidal element 37 from thediscoidal element 35 until the sectors 83 contact the lower bead P2 ofthe tire P, pushing it slightly away from the annular bead P1. Again,the annular bead P2 need not be perfectly concentric with the discoidalelement 37, as already mentioned with regard to the upper bead P1. Inthe next or sixth stage shown in FIG. 15, the actuator 39 turns theshaft 47 further in the same direction as before to complete thedilation of the discoidal elements 35 and 37: this places the pegs 65and the pegs 85 in contact with the beads P1 and P2, respectively, sothat the beads P1 and P2 and therefore the green tire P are exactlycentral with respect to the upper assembly 3A of the machine 3 andtherefore with respect to the machine structure and to all thecomponents of the mold 13, 15 and 17. In the seventh stage shown in FIG.16 the actuator 27 causes a further limited upward movement of thediscoidal element 35 to place the bead P1 of the tire in its exactposition against the corresponding profile of the pan or end plate 13 ofthe mold. In the next or eighth stage shown in FIG. 17, the lower pan orend plate 15 of the mold is moved up into contact with the lower bead P2of the tire P, which bead P2 has been positioned centrally by the pegs85 of the discoidal element 37 because of the final centrifugal movementof the sectors 83, in the same way as for the upper bead P1. In thissituation the tire is in complete contact with both pans or end plates13 and 15 of the mold and exactly coaxial with them. In the next orninth stage shown in FIG. 18, the two discoidal elements 35, 37 aremoved slightly toward each other, away from the beads P1 and P2 of thetire and the actuator 39 is used to reduce the diametrical dimension ofthe discoidal elements 35 and 37 by centripetal movement of the sectors61 and 83, resulting in the tenth stage shown in FIG. 19, in which thediscoidal elements 35 and 37 are returned to the minimum diametricaldimension. Hence in the eleventh stage for the discoidal elements 35 and37, they can be pulled back up under the bottom of the cup 25. Afterthis the pan or end plate 15 of the mold is moved into the position ofclosure of the mold as seen in FIG. 21, following which mold closure iscompleted by the sectors 17 advancing in the direction of arrows f17 inFIG. 21 to close the mold and allow curing to be carried out.

During the stages shown in FIGS. 16, 17 and 18 a “shaping” gas is fedinto the inside of the tire to stabilize the position of the green tireagainst the pans or end plates 13 and 15 of the mold so that the greentire P is maintained in the condition in which it was placed by thediscoidal elements 35 and 37 as described above.

Notice that when the annular edges or beads P1, P2 of the tire areplaced against the corresponding pans or end plates 13 and 15, saidbeads continue to be guided by the spring-loaded pegs 65 and 85, whichgradually withdraw into their respective sectors 61 and 83 as they abutagainst the pans or end plates 13 and 15.

The slight pressure of shaping gas inside the tire in the conditionsshown in FIGS. 16, 17 and 18 is obtained by supplying the shaping gasfrom a unit 101 outlined in the drawing and particularly in some of thefigures, while 109, 110, 111 are general references for means fordischarging the fluids from inside the tire for the shaping action andfor the compression inside the tire, which is effected by an elasticallydilatable sucker means for establishing the high curing pressure insidethe tire, in the mold in which the tire is to be cured, as will bedescribed later in two different embodiments. This gas supply throughthe unit 101 and this discharge through the unit 110 will take placepromptly at the moment when the beads P1 and P2 contact the two pans orend plates 13 and 15, to ensure this contact takes place until theinside of the tire has gradually filled with the elastic bladder means,which must reach the high pressures to bring about the compressioninside the tire for curing to take place. The elastic bladder must beallowed to dilate by removing the shaping gas at the correct rate.

The use of the dilatable discoidal elements, the slight pressure of the“shaping” gas and the subsequent dilation of the elastic bladder ensuresthat the tire P (which is in its green state and therefore very weak) isexactly central relative to the mold in which it is to be cured.

FIGS. 28–31 show a series of stages for the unloading of the tire afterits curing and for removing the tire to allow the next work cycle totake place. FIG. 28 shows the mold starting to open as the sectors 17withdraw in the opposite direction to the centripetal arrows f17 of FIG.21. The pan or end plate 15 of the mold is then lowered, as are the twodiscoidal elements 35 and 37 until they are positioned as shown in FIG.29 in the central region of the tire—the tire still being supported bythe pan or end plate 15. In this configuration the discoidal elements35, 37 are again dilated to the condition shown in FIG. 30, that isuntil the pegs 65 of the discoidal element 35 reach a radial distanceslightly less than the diametrical dimension of the bead P1, as seen inFIG. 30. As the pan or end plate 15 continues to descend, the tire endsup resting on the sectors 61 of the discoidal element 35 as seen in FIG.31, so that the tire can be deposited and collected by a conveyorindicated in a general way by the outline 120 in FIG. 31. This removalassembly may be a discharging roller conveyor or a pan which can beplaced underneath the tire to receive the tire and then transfer it inthe direction of arrow f120 for subsequent processing, the discoidalelement 35 being lowered slightly again, slightly shrunk in diametricaldimensions and then lifted back up toward the cup element 25.

FIGS. 35–44 show an example of a lower unit 3B of the machine 3 designedto insert into the tire, when the tire is housed in the mold, an elastictubular bladder which is supplied with fluid at high pressure tocompress the green rubber against the mold and allow the tire to becured, in a manner which is basically known per se.

An actuator 151A, 151B, 151C is provided for moving a lower core 153 towhich the elastic tubular bladder 155 is attached. An upper core 157grips the upper edge of the elastic tubular bladder 155. This core 157is controlled by an actuator 159A, 159B and 151C, this last being acommon part shared with the actuator 151A, 151B and 151C. A pipe 161supplies fluid at high pressure to the volume defined by the elastictubular bladder 155 and cores 153 and 157. During the stages shown inFIGS. 35, 36 and 37 the bladder 155 is raised into the tire and initialinflation of the bladder begins, at which time the shaping gas which wasfed in earlier as described above into the tire before and duringclosure of the mold must be discharged and must in fact be expelled whenthe interior of the tire is to be occupied by the dilated bladder asindicated in FIG. 38. The shaping gas must be expelled through the upperdischarge 110, and the similar lower discharge 109. Once in thecondition shown in FIG. 38, the mold is closed as shown in FIGS. 39 and40, compression inside the bladder 155 is completed, and the tireundergoes curing.

Following curing in the configuration shown in FIG. 40 the mold isreopened as shown in FIGS. 41 and 42 (having first discharged, through111, the pressurizing fluid from the bladder 155), leading back to theposition shown in FIG. 44 via the intermediate position shown in FIG.43.

FIGS. 45–54 show a different elastic bladder system for applying theinternal compression for curing purposes and for discharge from thisassembly.

This version uses in the first place a different mold closing systemconsisting of two pans or end plates 213, 215 and sectors 217 which havean inclined outer profile practically in frustoconical sections, to beacted upon by a frustoconical skirt 219 by which the mold is closed whenthe components 213, 215, 217 are lowered relative to the skirt 219. Thisform of mold is known per se. Another variant of the bladder system isrepresented by the mechanisms for moving the bladder, which areconstructed to reduce the vertical dimensions compared with the systemdescribed previously.

A base 230 supports guide columns 232 connected to correspondingdouble-acting fluid actuators, shown in a general way at 234, forraising and lowering a platform 236 to which the elastic tubular bladderassembly belongs. Extending from the lower part of the platform 236 is acolumn 238 carrying the upper core 240 to which the upper edge of thebladder 242 is attached.

The lower edge of the bladder 242 is attached to a lower core 244 whichslides up and down the column 238 independently of the upper core 240.The lower core 244 is moved up and down the column 238 by twosymmetrical toggles 246, 248 each having an intermediate hinge 250, anupper hinge 252 connected to the core 244 and a lower hinge 254 which isturned by one of a pair of gearwheels 256 that mesh with each other, onebeing powered by an actuator 258 hinged at 260 to the platform 236. Thisarrangement allows the core 244 to move up and down the column 238. Thevertical dimension of this assembly is very small.

From the initial position shown in FIG. 45, which depicts the firststage of the cycle of this system, the platform 236 is raised by theactuators 234 along the columns 232 to the position shown in FIG. 46,where the upper core 240 is basically inside the tire P between the openmold components. The actuator 258 then immediately raises the core 244by means of the two toggles 246, 248, 250 to the position shown in FIG.47, in which the bladder, which has already partly begun to fill withthe compression fluid, dilates inside the tire P. At this point (seeFIG. 48) the end plate 213 moves down toward the end plate 215 andslightly squeezes the partially dilated bladder 242. As can be seen inFIG. 49, a tubular-walled diaphragm 270 is lowered to allow a more evendilation of the bladder 242 inside the tire until we reach the positionshown in FIG. 50, in which the bladder 242 has reached the inside wallof the tire. FIG. 51 shows the position with the mold closed, closureoccurring as the actuators 234 lower the platform 236 and due to theinternal inclination of the skirt 219 pushing the sectors 217 in untilthe mold is closed. It is in these conditions shown in FIG. 52 thatcuring takes place, followed by opening of the mold as shown by thesequence of figures coming after FIG. 51 and up to FIG. 54, in which thetoggles return the bladder to the condition illustrated earlier in FIG.45 and the mold is opened to allow the cured tire to be taken hold ofand lifted out for transfer to subsequent processing.

This latter version reduces the vertical size of the machine, which ismuch greater when using the arrangement shown in FIGS. 35–44.

It will be understood that the drawing shows only an example purely as apractical demonstration of the invention, and that the invention can bevaried in its shapes and arrangements without thereby departing from thescope of the concept on which the invention is based. The presence ofany reference numbers in the appended claims is for the purpose offacilitating the reading of the claims with reference to the descriptionand to the drawing, and does not limit the scope of protectionrepresented by the claims.

1. Machine for curing green rubber in the production of tires for roadvehicles and the like, comprising a mold with two circular pans or endplates and peripheral sectors defining the tread, and with bladder meansfor creating a pressure inside the tire, and with two opposeddiametrically dilatable coaxial discoidal elements that are able to passaxially from the top into the tire when the tire is positioned in themold, characterized in that: said two opposed discoidal elements areable to move independently of each other axially; said discoidalelements have sectors that can be moved radially forming horizontalcontact surfaces for engaging from the inside the annular beads of thetire, when said discoidal elements are moved one from the other; thatsaid sectors of said discoidal elements have moreover spring loadedvertical pegs for radially making contact with the inner edge of theannular beads of the tires and that are able to retract on contact withthe circular pans or end plates of the mold when said discoidal elementsapproach the respective circular pans or end plates of the mold; meansare provided for supplying a shaping gas at limited pressure into thetire while the two pans are being moved toward each other during moldclosure; and means are provided for discharging at the appropriate timesaid shaping gas from inside the tire when said bladder means areexpanded from inside the tire.
 2. Machine according to claim 1,characterized in that said sectors are radially movable and operated byshaped links pivoting on an angularly movable actuator disk coaxial withsaid discoidal elements.
 3. Machine according to claim 1, characterizedin that it comprises, for bringing about the axial movements of saiddiscoidal elements: a first actuator for lowering both of said discoidalelements into the tire, and raising them again; and a second actuatorfor axially moving one of said discoidal elements with respect to theother.
 4. Machine according to claim 1, comprising control means forradially moving said sectors characterized in that said control meansare able to bring about a partial dilation before the axial movement tocontact the respective annular bead of the tire, followed by a furtherdilation to make radial contact with the edge of said bead, by means ofsaid spring-loaded pegs.
 5. Machine according to at least claim 1,characterized in that said bladder means are tubular in shape, andinclude two annular edges engaged on movable members of two axialactuators capable of positioning the bladder means in the mold in theclosed position; means being provided for supplying a fluid at pressureinto the bladder means for the molding and curing stage.
 6. Machineaccording to claim 5, wherein said axial actuators are twocylinder-and-piston systems.
 7. Machine according to claim 5,characterized in that one of said axial actuators is in the form of acylinder-and-piston system which raises a bladder assembly and the otherof said axial actuators comprises two symmetrical toggles controlled bya gear pair mechanism controlled by a single fluid actuator.
 8. Machineaccording to claim 2, characterized in that it comprises, for bringingabout the axial movements of said discoidal elements: a first actuatorfor lowering both of said discoidal elements into the tire, and raisingthem again; and a second actuator for axially moving one of saiddiscoidal elements with respect to the other.
 9. Machine according toclaim 2, comprising control means for radially moving said sectorscharacterized in that said control means are able to bring about apartial dilation before the axial movement to contact the respectiveannular bead of the tire, followed by a further dilation to make radialcontact with the edge of said bead, by means of said spring-loaded pegs.10. Machine according to claim 3, comprising control means for radiallymoving said sectors characterized in that said control means are able tobring about a partial dilation before the axial movement to contact therespective annular bead of the tire, followed by a further dilation tomake radial contact with the edge of said bead, by means of saidspring-loaded pegs.
 11. A machine for curing green rubber in theproduction of tires for vehicles, said machine comprising: a mold havingtwo circular pans or end plates and peripheral sectors defining a tread;a bladder means for creating a pressure inside a tire; two opposeddiametrically dilatable coaxial discoidal elements passing axially froma top into the tire when the tire is positioned in said mold, said twoopposed discoidal elements being independently axially movable relativeto each other, said discoidal elements having sectors that move radiallyto form horizontal contact surfaces for engaging annular beads locatedon the tire when said discoidal elements are moved relative to oneanother, said sectors having spring-loaded vertical pegs for radiallymaking contact with an inner edge of the annular beads of the tire, saidsectors retracting on contact with said circular pans or end plates ofsaid mold when said discoidal elements approach said circular pans orend plates of said mold; a means for supplying a shaping gas at limitedpressure into a tire while said circular pans or said end plates movetoward each other during mold closure; and a means for discharging saidshaping gas from inside the tire when said bladder means expands withinthe tire.
 12. A machine in accordance with claim 11, wherein saidsectors that are radially movable and operated by shaped links pivotingon an angularly movable actuator disk coaxial with said discoidalelements.
 13. A machine in accordance with claim 11, further comprising:a first actuator for lowering both of said discoidal elements into thetire, and raising them again; and a second actuator for axially movingone of said discoidal elements with respect to the other.
 14. A machinein accordance with claim 11, further comprising a control means forradially moving said sectors, wherein said control means brings about apartial dilation before axial movement to contact the respective annularbead of the tire, followed by a further dilation making radial contactwith the edge of said bead by means of spring-loaded pegs.
 15. A machinein accordance with claim 11, further comprising a means for supplying afluid at pressure into said bladder means during a molding and curingstage, said bladder means being tubular in shape, and including twoannular edges engaging on movable members of two axial actuatorspositioning said bladder means in said mold in a closed position.
 16. Amachine in accordance with claim 15, wherein said axial actuators aretwo cylinder-and-piston systems.
 17. A machine in accordance with claim15, wherein one of said axial actuators is a cylinder-and-piston systemthat raises a bladder assembly and the other of said axial actuatorscomprises two symmetrical toggles controlled by a gear pair mechanism,said gear pair mechanism being controlled by a single fluid actuator.18. A machine for curing rubber, said machine comprising: a mold havingtwo circular pans or end plates and peripheral tread sectors; a bladdermeans for creating a pressure inside a tire after the tire is placedwithin said mold; and two opposed upper and lower independently axiallymovable coaxial discoidal elements being independently axially movablerelative to each other, said discoidal elements passing axially from thetop of the tire positioned in said mold, said discoidal elements havingradially movable sectors contacting annular beads on an inner edge ofthe tire, said radially movable sectors retracting after contacting saidcircular pans or end plates of said mold when said discoidal elementsapproach said circular pans or said end plates of said mold.
 19. Amachine in accordance with claim 18, further comprising a means forsupplying a shaping gas at limited pressure into a tire while saidcircular pans or said end plates move toward each other during moldclosure.
 20. A machine in accordance with claim 18, further comprising ameans for discharging a shaping gas from inside the tire when saidbladder means expands within the tire.